In television broadcasting stations etc., the video tape recording (VTR) apparatuses, video editing apparatuses, etc. used for the editing of videos are connected via a routing apparatus. A digital video signal and an audio video signal transmitted from any apparatus are input to a desired other apparatus via the routing apparatus and used for editing etc.
The routing apparatus selects a signal which has been input to a specific input terminal of a plurality of input terminals and outputs it to any output terminal of a plurality of output terminals. That is, the routing apparatus acts as a switching apparatus which outputs a certain input signal to any output terminal to which a specific apparatus is connected. This switching operation is called the routing of the routing apparatus.
As the transmission format for transmitting a digital video signal and a digital audio signal (hereinafter, the digital video signal and the digital audio signal are referred to overall as digital data or a digital AV signal) between editing apparatuses used for the editing of the video signal etc., the serial digital interface (SDI) format has been known.
The SDI format is standardized in the SMPTE-295M standard of the SMPTE (Society of Motion Picture and Television Engineering).
This SMPTE-2 standard is basically a signal standard for the D1 format or D2 format which are the standards of digital signals. Accordingly, a signal of the SDI format is also used for transmission as a digital AV signal of the D1 format or D2 format. The transmission speed (transmission frequency) of the signal of the SDI format is a high speed, i.e., 270 MHz. However, for standardization, the amount of a signal of the SDI format which can be transmitted is restricted to only one channel's worth of the digital video signal and further restricted to only eight channels' worth of the base band audio signal. For this reason, when using an SDI signal, the user sometimes encounters the limits of transmission. A signal of the SDI format is not always suitable for meeting with the demands of multimedia or multi-channels which are now growing in the field of broadcasting or editing of videos.
Therefore, the assignee of the present application has proposed a novel format of digital data which is not only suitable for the multimedia or multi-channel while making active use of the advantages of the SDI format and maintaining partial commonality with the SDI format, but is also suitable for transmission in a data communication system such as a local area network (LAN), Ether Net, or Token Ring (for example, refer to Japanese Patent Application No. 6-144403 entitled "Digital Signal Transmission Method, Digital Signal Transmission Apparatus and Receiving Apparatus, and Transmitting and Receiving Apparatus" filed before the Japanese Patent Office on Jun. 27, 1994). This new transmission format proposed by the present assignee is referred to as the "serial digital data interface (SDDI)" format. Details of this SDDI format (trademark of Sony Corporation) will be explained later.
As the digital AV signal in the editing process of a television broadcasting station etc., there is a case where a signal of the SDI format and a signal of the SDDI format are mixed. Accordingly, it is necessary to suitably route these mixed signals of the SDI format and SDDI format in the routing apparatus to transmit the data to the intended editing apparatus and, at the same time, necessary to perform the editing using the signal of the SDI format and the signal of the SDDI format with a good efficiency.